1Now about that time, King Herod stretched out his hands to oppress some of the assembly. 2He killed James, the brother of John, with the sword. 3When he saw that it pleased the Jews, he proceeded to seize Peter also. This was during the days of unleavened bread. 4When he had arrested him, he put him in prison and delivered him to four squads of four soldiers each to guard him, intending to bring him out to the people after the Passover. 5Peter therefore was kept in the prison, but constant prayer was made by the assembly to God for him. 6The same night when Herod was about to bring him out, Peter was sleeping between two soldiers, bound with two chains. Guards in front of the door kept the prison.
7And behold, an angel of the Lord stood by him, and a light shone in the cell. He struck Peter on the side and woke him up, saying, “Stand up quickly!” His chains fell off his hands. 8The angel said to him, “Get dressed and put on your sandals.” He did so. He said to him, “Put on your cloak and follow me.” 9And he went out and followed him. He didn’t know that what was being done by the angel was real, but thought he saw a vision. 10When they were past the first and the second guard, they came to the iron gate that leads into the city, which opened to them by itself. They went out and went down one street, and immediately the angel departed from him.
11When Peter had come to himself, he said, “Now I truly know that the Lord has sent out his angel and delivered me out of the hand of Herod, and from everything the Jewish people were expecting.” 12Thinking about that, he came to the house of Mary, the mother of John who was called Mark, where many were gathered together and were praying. 13When Peter knocked at the door of the gate, a servant girl named Rhoda came to answer. 14When she recognized Peter’s voice, she didn’t open the gate for joy, but ran in and reported that Peter was standing in front of the gate.
15They said to her, “You are crazy!” But she insisted that it was so. They said, “It is his angel.” 16But Peter continued knocking. When they had opened, they saw him and were amazed. 17But he, beckoning to them with his hand to be silent, declared to them how the Lord had brought him out of the prison. He said, “Tell these things to James and to the brothers.” Then he departed and went to another place.
18Now as soon as it was day, there was no small stir among the soldiers about what had become of Peter. 19When Herod had sought for him and didn’t find him, he examined the guards, then commanded that they should be put to death. He went down from Judea to Caesarea, and stayed there.
20Now Herod was very angry with the people of Tyre and Sidon. They came with one accord to him and, having made Blastus, the king’s personal aide, their friend, they asked for peace, because their country depended on the king’s country for food. 21On an appointed day, Herod dressed himself in royal clothing, sat on the throne, and gave a speech to them. 22The people shouted, “The voice of a god, and not of a man!” 23Immediately an angel of the Lord struck him, because he didn’t give God the glory. Then he was eaten by worms and died.
24But the word of God grew and multiplied. 25Barnabas and Saul returned to Jerusalem when they had fulfilled their service, also taking with them John who was called Mark.
There is uncertainty as to whether the Upper Room spoken of in Acts 1:13 is the same one that was used by the twelve disciples and Jesus on the night of the Last Supper before His betrayal, in the Upper Room (Matt 26:17-35), or the place the apostles were meeting discussed in Luke 24:33-48. It might also be the one that is spoken of in Acts 1:13. Since Mary, the mother of Jesus, as well as His brothers, were there, it may be that this was their home in Jerusalem, mentioned in Acts 12:12. We simply can't tell from the text. The night of the meeting of the 120, the apostles, some women, Mary, the mother of Jesus, and James and John had gathered. Several matters were discussed, including the betrayal and death of Judas (1:16-20), and the successor to Judas (1:21-26).
At least two possible sites are found in Jerusalem that may have been the Upper Room of the Last Supper or the one in Acts 1, possible house of Mary. There is tradition for both, but the evidence is inconclusive. See photos at Acts 1:13 for these two sites: the Upper Room and traditional house of Mark in the Syrian Orthodox St. Mark's Convent, or the Upper Room above David's alleged tomb on Mt. Zion near the Temple Mount.